A survey of benthic invertebrates and associated environmental factors was carried out in three Southland streams in relation to developed and undeveloped pasture over 15 months in 1985— 1987. In all three streams the invertebrate community changed in the sections within developed pasture in such a way as to suggest pollution, although no point sources were present. Numbers ofDeleatidiumspp.,Pycnocentrodes aureola, Olingaferedayi, Archichauliodes diversus, Aoteapsyche colonica, and Plecoptera tended to decrease in the developed pasture area, whereas numbers ofPotamopyrgus antipodarum, Physastra variabilis, Gyraulus corinnaand Oligochaeta tended to increase. Stepwise regression was carried out on six environmental variables vs seven of the more numerous taxa. Significant regressions atP <0.01 were obtained for 7 out of 21 instances, but little consistency was apparent across streams or taxa. The significant regressions that were obtained did not explain readily the tendency towards a pollution‐type community, and it is suggested that dips and drenches used on sheep in the developed pastures could be partly responsible for some of the changes.